NOAH Compendium

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Date: Thursday, December 2, 2021 16:08

Release 2.48
Epiphen Solution 4% w/v, Oral Drops
Species: Dogs
Therapeutic indication: Pharmaceuticals: Neurological preparations: Others
Active ingredient: Phenobarbital
Product:Epiphen Solution 4% w/v, Oral Drops
Product index: Epiphen Solution
Oral solution.
A clear, colourless, slightly viscous liquid containing 4% w/v Phenobarbital
Phenobarbital is an antiepileptic agent for use in the control of epilepsy in the dog.
Dosage and administration
The required dosage will differ to some extent between individuals and with the nature and severity of the disorder.
Dogs should be dosed orally, starting with a dose of 2.5 - 5.0 mg/kg (0.06 - 0.125ml per kg) bodyweight per day. The dose should be divided and administered twice daily using the 2ml syringe provided. 1ml contains 40mg of phenobarbital.
Weight of dog
Volume of Epiphen Solution/day*
Dosage range mg/kg
1- 1.5 kg
2.7 - 4.0
2-3 kg
2.7 - 4.0
4 - 5 kg
3.2 - 4.0
6 - 9 kg
3.1 - 4.7
10 - 15 kg
1.2 ml
3.2 - 4.8
16 - 20 kg
1.6 ml
3.2 - 4.0
*The dose should be divided and administered twice daily.
Steady state serum concentrations are not reached until 1 - 2 weeks after treatment is initiated. The full effect of the medication does not appear for two weeks and doses should not be increased during this time.
If seizures are not being controlled, the dosage may be increased by 20% at a time, with associated monitoring of serum phenobarbital levels. The phenobarbital serum concentration may be checked after steady state has been achieved, and if it is less than 15 µg/ml the dose may be adjusted accordingly. If seizures recur the dose may be raised up to a maximum serum concentration of 45 µg/ml. High plasma concentrations may be associated with hepatotoxicity. Blood samples should be taken at the same time to allow plasma phenobarbital concentration to be determined, preferably during trough levels shortly before the next dose of phenobarbital is due.
Contra-indications, warnings, etc
Not for use in pregnant animals or nursing bitches.
Do not administer to animals with impaired hepatic function.
Special precautions for use in animals
Withdrawal of phenobarbital or transition to, or from, another type of antiepileptic therapy should be made gradually to avoid precipitating an increase in the frequency of seizures.
Special precautions to be taken by the person administering the veterinary medicinal product
In case of accidental ingestion, seek medical attention immediately advising medical services of barbiturate poisoning, or show the container.
Flammable, keep away from sources of ignition. Do not smoke.
Wash hands after use.
Adverse reactions (frequency and seriousness)
Occasionally polyphagia, polyuria and polydipsia have been reported, but these effects are usually transitory and disappear with continued medication.
Toxicity may develop at doses over 20mg/kg/day or when serum phenobarbital levels rise above 45µg/ml.
In the light of isolated reports describing hepatotoxicity associated with combination anticonvulsant therapy, it is recommended that:-
1.Hepatic function is evaluated prior to initiation of therapy (e.g. measurement of serum bile acids).
2.Therapeutic phenobarbital serum concentrations are monitored to enable the lowest effective dose to be used. Typically concentrations of 15 - 45µg/ml are effective in controlling epilepsy.
3.Hepatic function is re-evaluated on a regular (6 to 12 month) basis.
4.Seizure activity is re-evaluated on a regular basis
Use during pregnancy and lactation
In humans, mothers receiving antiepileptic medication have a 6 to 10% incidence of significant abnormality in their offspring. Neonatal sedation and drug dependence may occur if given close to term. Phenobarbital crosses the placental barrier and small amounts are excreted in breast milk. Therefore, phenobarbital is contraindicated in pregnancy and nursing bitches.
Interaction with other medicinal products and other forms of interaction
Phenobarbital will potentially reduce therapeutic levels of a wide range of drugs due to its inducing effect on hepatic enzymes.
Phenobarbital may reduce the activity of some drugs by increasing the rate of metabolism through induction of drug-metabolising enzymes in liver microsomes.
Use of phenobarbital in conjunction with primidone is not recommended as primidone is predominantly metabolised to phenobarbital.
Overdose (symptoms, emergency procedures, antidotes), if necessary
Overdosage may result in coma, severe respiratory and cardiovascular depression, hypotension and shock leading to renal failure and death.
Following the recent ingestion of an overdose, the stomach may be emptied by lavage.
The prime objectives of management are then intensive symptomatic and supportive therapy with particular attention being paid to the maintenance of cardiovascular, respiratory and renal functions and to the maintenance of the electrolyte balance.
Withdrawal period(s)
Not applicable
Pharmaceutical precautions
Do not store above 25°C.
Protect from light.
Store in tightly closed original container.
Any unused product must be destroyed in accordance with the Misuse of Drugs Regulations (2001). Any waste material should be disposed of in accordance with local requirements.
Legal category
Legal category: POM-V
Legal category description:CD(Sch 3)
Packaging quantities
30ml presentation
amber glass vial of type II
polyethylene syringe applicator
medium density child proof polyethylene cap
2ml polypropylene graduated syringe
Further information
The antiepileptic effects of phenobarbital are probably the result of at least two mechanisms: - Decreased monosynaptic transmission, which presumably results in reduced neuronal excitability and an increase in the motor cortex's threshold for electrical stimulation.
After oral administration of phenobarbital to dogs, the drug is rapidly absorbed and maximal plasma concentrations are reached within 4 - 8 hours. Bioavailability is between 86% - 96%. About 45% of the plasma concentration is protein bound. Metabolism is by aromatic hydroxylation of the phenyl group in the para position, and about one third of the drug is excreted unchanged in the urine. Elimination half-lives vary considerably between individuals and range from about 40 - 90 hours.
Marketing Authorisation Number
UK: Vm 08007/4081
Significant changes
GTIN description:Epiphen Solution